1. Field of Invention
This invention relates to a novel method for remodeling of the femoral head and to prosthetic means, including an intramedullary insert and integral shell or cap, for use as a part of the said femoral head remodeling procedure.
The ultimate product of the present invention may be employed with an intact acetabula, namely, the cup-shaped socket in the hip bone, or in combination with prosthetic acetabular sockets or cups, which are widely available from orthopaedic supply organizations today and which are well known in the art. A representative prosthetic acetabular socket is disclosed in U.S. Pat. No. 3,722,002. Representative orthopaedic supply houses specializing in prosthetic acetabular sockets include DePuy, Howmedica, and Zimmer, the latter of which also specializes in Amstutz-developed femoral head prosthetic devices and total hip joint replacement prosthetic components.
As is well known in the art, the hip joint comprises the acetabula or an acetabular prosthesis, which is a cup-shaped socket in the hip bone, providing a generally hemispheric surface, within which the femoral head, having a corresponding generally hemispheric surface contour, rotates by means of a thin layer of cartilage under normal conditions and on a thin layer of plastic or the like under conditions of reconstruction and prosthesis after the normal cartilage has become eroded or the hip joint has become otherwise inoperative due to aging, inury, or other abnormal conditions arising from any of a multitude of etiologies.
The ultimate product of the present invention, which is a femur having a remodeled femoral head including prosthetic means comprising the intramedullary insert and its integral cap, is intended for use in cooperation with a normal or prosthetic acetabular socket, but the provision of such acetabular socket does not constitute a part of the present invention.
2. Prior Art
The prior art is replete with procedure and prosthetic means for remodeling of the femoral head. Most of the intramedullary inserts are curved and have a ball at the upper end to replace the femoral head itself. Further, most procedures and prosthetic means for implementing the same involve resection of the femoral head at a point just above the lesser trochanter at approximately the calcar or inferior neck of the femur, the resection being made on an angle approximately 45 degrees from the horizontal and commencing just above the greater trochanter and ending at the calcar or inferior neck of the femur just above the lesser trochanter. However, in many instances, such resection results in the elimination of considerable healthy cancellous bone and cortex of the femoral head and otherwise lying above the lesser trochanter and calcar, with the result that maximum utilization of existing and utilizable portions of the femur lying above the lesser trochanter and calcar is not effected. Further, according to most prior art procedures and prosthetic devices therefor, the intramedullary insert is usually inserted into the intramedullary canal or femoral shaft at an angle, and only a relatively small portion thereof is in line with the vertical axis of the intramedullary canal or femoral shaft, providing less than maximum support for the femoral insert within the femoral shaft and remodeled femur. Additionally, such femoral inserts have been less than adequately stabilized in their desired position within the femoral shaft, resulting in a twisting, turning, and displacement effect after the remodeled femur has been placed into use. Further, the existing procedures and femoral inserts have failed to provide an osteotomy and femoral insert in which the opposing surface angles in the remodeled femoral head are essentially perpendicular to the lines of force imparted by the hip during normal gait, thereby to decrease the shear force applied to the remodeled femoral head and resulting in inherent stability thereof in actual use of the remodeled femur.
Representative U.S. Patents in this field include No. 3,314,420, which shows a porous ceramic body formed of one material which can be used in the creation of a femoral insert; No. 3,510,883, which shows a typical femoral insert including femoral head, just as does the earlier-cited patent Nos.; Nos. 3,694,820; 3,744,061; 3,781,917; 3,808,606, which shows a type of porous coating which can be employed on a femoral insert; Nos. 3,815,590; 3,843,975; 3,855,638, which again shows a porous coating which may be employed on the external surface of a femoral insert; No. 3,893,196, which shows another material of construction which can be used for a femoral insert; Nos. 3,922,726; 3,925,824; 3,938,198, which presents a detailed review of the art; No. 3,965,490, which relates to commercially-available prosthetic means and discloses certain alloys which can be used as material of construction for femoral inserts; No. 4,012,796, which shows a femoral insert having an "interpositioning collar"; 4,021,865, which employs a flange and serrations to impede separation of the insert from the femoral shaft; No. 4,035,848, which discloses a specific hip capitulum cap; No. 4,064,567, which discloses a woven basket cover for the prosthetic device to improve the gripping surface thereof; No. 4,068,324, which discloses a combination of an artificial femoral head and acetabular socket; No. 4,123,806, which provides an excellent review of the prior art and medical terms involved; No. 4,141,088, which discloses a representative femoral insert; No. 4,156,943, which discloses another porous material which may be employed in the production of a femoral insert; and No. 4,206,516, which discloses another porous coating, in this case a metal porous coating, which may employed on the outer surface of a femoral implant to support ingrowth of bone tissue for fixation of the device within the femoral shaft.